The present invention broadly relates to industrial vehicles and, more specifically, pertains to a new and improved construction of a collision protection device for industrial vehicles.
Generally speaking, the present invention relates to a collision protection device for industrial vehicles, wherein a moveable or displaceable collision protector or bumper which extends at least over the whole or overall width of the vehicle and which is retained in a rest position by means of spring force cooperates with a de-energizing device. The de-energizing device triggers a vehicle stopping operation when the collision protector collides against an obstacle and is consequently moved against the spring force. The collision protector initially effects a short actuation movement or throw displacement of sliding link members when, in turn, cause actuation of the de-energizing device. While the vehicle is being retarded or decelerated, the collision protector subsequently implements a longer throw displacement of these sliding link members during which time it is ensured that the de-energizing device still remains activated.
In other words, the collision protection device of the present invention is for protecting industrial vehicles, especially industrial trucks such as fork-lift trucks, warehouse transport trucks and storage system robots, against collision with an obstacle or another vehicle. The collision protection device comprises a displaceable collision protector or bumper having a rest position and a de-energizing device or switch means cooperating with the displaceable collision protector or bumper. The industrial vehicle has an overall width and the displaceable collision protector or bumper extends at least over the overall width of the industrial vehicle. The collision protection device comprises at least one spring means for generating a biasing force and means enabling the biasing force to retain the displaceable collision protector in the rest position. The de-energizing device has means for causing the industrial vehicle to stop when the displaceable collision protector is moved against the biasing force by collision with the obstacle. The collision protection device has means enabling the displaceable collision protector to effect an initial actuating movement of the de-energizing device and, while the industrial vehicle is being subsequently retarded, implementing a continuation of such actuating movement during which the de-energizing device remains activated.
Such collision protection devices prevent, to a large extent, damage when the vehicle collides against an obstacle, be this a fixed obstacle or a moving obstacle. Collision protection devices must consequently ensure faultless operation, especially so because they are an integral part of automatic, driverless industrial vehicles or robots. For such industrial vehicles, the existence or unexpected appearance of an obstacle is difficult to recognize.
A collision protection device of this general type is mentioned in the German periodical "Automatik" of April 1959, pages 108 and 113. It comprises a collision protector which consists of a rounded-off frame which is fixed on the front of the vehicle by means of a sprung or resilient mount. When the vehicle strikes an obstacle, the collision protector, which is moved against the spring force, activates two microswitches by means of which the vehicle drive is switched off and by which the brakes are activated. By means of the resilient mounting apparatus, the collision protector can move beyond the actuation position of the microswitch in the same manner as the vehicle continues to move due to its inertia after the stop command.
This apparatus which is assembled from a rounded-off, displaceable frame with a support or bracket and which can be steered from the vehicle chassis, can prove to be advantageous if the collision protector collides with an obstacle along the longitudinal axis of the vehicle, and especially if the vehicle possesses only one steerable wheel which is mounted in the middle of the steerable support. The effectiveness of the apparatus becomes questionable as soon as the impact occurs slightly laterally of the collision protector, i.e. eccentrically. This is especially so if the vehicle is equipped with two steerable wheels and if the collision protector is mounted on a fixed component on a vehicle chassis member.
From the German Patent No. 1,781,159, published Apr. 22, 1971 an apparatus is known with which the above-mentioned disadvantages are avoided in that the collision protector comprises a tube arranged as a loop. The tube is constructed out of a flexible or extensible, i.e. elastic material and is filled with a fluid. When any point of the collision protector collides with an obstacle, the pressure change brought about by the deformation of the tube is used to actuate the de-energizing device which triggers a vehicle stop, for instance by means of a membrane.
The main disadvantage of this collision protection device consists in the relative vulnerability of the tube which is constructed of a flexible material. Even in a reinforced embodiment, the tube can be damaged in a collision against an obstacle or can be punctured by sharp objects. Its de-energizing function is then no longer ensured. Furthermore, such a tubular collision protector can only offer protection in a limited vertical range. Moreover, because of its elasticity, it is less suitable for severe impacts than a rigid collision protector.
A further apparatus which is disclosed in the West German Patent Publication No. 1,655,813 and in which the above-mentioned disadvantages are avoided, comprises an elastic collision protector with a ring-like or annular loop whose rounded-off ends are connected with a steerable support or carrier mounted on the front side of the vehicle. Furthermore, the flexible collision protector is connected at two points on its perimeter with the steerable support by means of a de-energizing device which comprises two telescopic, slidable parts. A cam located on one of the two parts actuates a switch mounted on the second part. When the switch is actuated, a vehicle stop is triggered.
The main disadvantage of this apparatus consists in the risk that the collision protector will be deformed beyond its elasticity in a severe collision with an obstacle and/or by the delayed stopping of the vehicle due to its inertia. In this manner, the apparatus could be damaged and the switches could be blocked which would prevent switching the vehicle drive motor on again.